An anastomosis is an connection between two structures, organs or spaces. It most commonly refers to a connection which is created surgically between two tubular structures, such as a transected blood vessel or loop of intestine. For example, when a segment of intestine is resected, the two remaining ends are sewn or stapled together (anastomosed), and the procedure is referred to as an intestinal anastomosis. Anastomoses also occur normally in the body in the circulatory system, serving as backup routes for blood to flow if one link is blocked or otherwise compromised.
Examples of surgical anastomoses are colostomy (an opening created between the bowel and the abdominal skin) and arterio-venous fistula (an opening created between an artery and vein) for hemodialysis.
A pathological anastomosis can result from trauma or disease and may involve veins, arteries, or intestines. These are usually referred to as fistulas. In the cases of veins or arteries, traumatic fistulas usually occur between artery and vein. Traumatic intestinal fistulas usually occur between two loops of intestine (enetero-enteric fistula) or intestine and skin (enterocutaneous fistula).